Add PyPI downloads badge to README

Added a badge for PyPI downloads to the README.

Author: ss0832

README.md

@@ -9,6 +9,7 @@
 
 [![Buy Me A Coffee](https://img.shields.io/badge/Buy%20Me%20a%20Coffee-ffdd00?style=for-the-badge&logo=buy-me-a-coffee&logoColor=black)](https://buymeacoffee.com/ss0832)
 
+[![PyPI Downloads](https://static.pepy.tech/personalized-badge/multioptpy?period=total&units=INTERNATIONAL_SYSTEM&left_color=BLACK&right_color=GREEN&left_text=downloads)](https://pepy.tech/projects/multioptpy)
 
 If this tool helped your studies, education, or saved your time, I'd appreciate a coffee!
 Your support serves as a great encouragement for this personal project and fuels my next journey.